California Code
ARTICLE 7 - Flashing and Colored Lights
Section 25277.

25277. Any vehicle used by any police department, sheriff’s office, or other governmental agency for the purpose of enforcing parking laws contained in the Vehicle Code or in a local ordinance or regulation may display flashing or revolving amber warning lights to the front, sides, or rear of the vehicle when actually engaged in the enforcement of such laws and when either necessarily stopped on a street, or when moving at a speed slower than the normal flow of traffic.

(Added by Stats. 1976, Ch. 234.)